The present invention relates generally to drainage means and drainage systems employed therefore, and more particularly to a novel drainage system construction incorporating cascading chutes which create an inner channel from which collected fluid cannot escape to re-infiltrate surrounding soil prior to its discharge point.
Where it is indicated by the terrain, soil structure, climate, landscaping or construction activities, it is often desirable or necessary to provide a drainage means for collecting and relocating moisture accumulating on the surface and moisture saturating the ground. By controlling the accumulation of surface moisture and moisture saturation of the ground, undesirable erosion, settling, and soil expansion are reduced. Such drainage means are often utilized surrounding and underneath buildings, rights of way such as highways, golf courses, athletic fields, recreational areas and similar applications.
A variety of drainage means suitable for use in collecting of surface moisture and moisture saturation of the ground are well known in the prior art, however, none have been entirely effective.
A predominant drainage means of the prior art is the use of so-called french drain systems. In constructing a french drain system, one or more trenches are dug in the ground with the trench or trenches sloping downward toward a collection point. Perforated pipe is then laid with fall sloping toward the discharge point, within a bed of gravel in the trench. Turf, landscaping, or construction structures may then be placed upon or around the gravel filled trench. In such a drain system, water is supposed to enter the pipe through the perforations and flow through the pipe by gravitational force to an outlet or pump at the discharge point; however, in operation, often times the water flows toward the discharge point within the gravel outside the pipe; this water, flowing within the gravel outside the pipe toward the collection point, re-infiltrates the soil at less saturated intermediate points. Additionally, as a result of the design of the system, water within the pipe cannot be contained within the pipe, and in operation, collected water within the pipe often exits the pipe and re-infiltrates the soil at less saturated intermediate points toward the discharge point. As a result of this re-infiltration of water, soil stability along the length of the drain system is not maintained and the soil continues to expand and contract from variations in moisture saturation. Additionally, the flow of water toward the discharge point within the gravel outside of the pipe, results in deterioration of the trench.
A typical modified form of a french drain system incorporates the use of permeable material, such as landscape fabric, to shield the gravel and pipe from silt and fine sediment which tend to accumulate in the pipe and gravel, gradually diminishing the effectiveness of the system. However, in application, the permeable material often becomes congested with the silt and fine sediment resulting in an increase in the effective hydrostatic pressure of the surrounding soil. Also, impermeable material has been applied to the bottom surface of the trench, below the perforated pipe, to protect it from the deteriorating effect of water flowing through the gravel outside of the pipe. However, the application of such impermeable material to the bottom of the trench has the undesirable effect of creating a barrier which prevents drainage of moisture from below the impermeable material which would otherwise percolate upwards. U.S. Pat. Nos. Re. 20,736 and 2,135,103 to Dimrick, which may be placed in a gravel filled trench, disclose a drainage pipe with inclined upper trough sections which empty into a lower pipe cavity at the termination of each trough section. Water is meant to be caught by the trough sections on the upper surface and emptied into the lower pipe cavity. With the drainage pipe according to Dimrick, it is apparent that silt and sediment that wash down through the gravel will quickly accumulate in the upper trough section and lower pipe cavity; further as water is collected by the Dimrick device at its upper surface, unless the water falls directly into the trough, sufficient hydrostatic pressure must accumulate for the water level to reach the top of the pipe before the water is collected. Additionally, the Dimrick device does not prevent the flow of water through the gravel toward the discharge point outside of the upper trough or lower cavity.
U.S. Pat. No. 2,663,997 to Schmidt et al. discloses a drainage tube, which may be set in a gravel filled trench, having inlet passageways that are protected by an overhanging cover. Although the Schmidt device is designed to alleviate the accumulation of silt and sediment by requiring that water must rise to enter the drainage tube, its very design necessitates the undesirable result that sufficient hydrostatic pressure be present to cause the water level to rise to the height of the inlet passageways. Additionally, the Schmidt et al. device does not prevent water flowing through the gravel toward the discharge point outside the tube.
As a final illustrative example of drainage means of the prior art that is suitable for use in a gravel filled trench, U.S. Pat. No. 4,389,138 to Soderstrom discloses a drainage system having a pipe that is divided into a central channel and two peripheral channels. The central channel is open at its lowermost end and the peripheral channels are closed at their lowermost end. The central channel is separated from each peripheral channel by a partition wall having openings in their uppermost ends. Additionally, the use of plugs at intervals along the central channel to create barriers to flow along the central channel to the discharge point is disclosed. Although the Soderstrom device prevents water from flowing to the discharge point through the gravel outside the pipe, excess hydrostatic pressure is necessary in operation of the device as the water level must rise to the level of the openings in the partition wall.
Accordingly, it is an object of the present invention to provide an improved drainage means, for collecting and relocating moisture accumulating on the surface and moisture saturating the ground, which does not require excess hydrostatic pressure in operation, isolates the water collected from re-infiltration and does not possess the shortcomings of the prior art drainage devices.
An additional objective of the present invention is to provide an improved drainage means that may be constructed from low cost and readily available construction materials.
The objects of the present invention are obtained by a drainage system construction incorporating cascading chutes, which collect moisture at their leading ends and form an inner channel from which the collected moisture cannot escape to re-infiltrate soil surrounding the drainage system prior to reaching the discharge point of the drainage system.
Although the present invention is hereinafter being described with reference to its application within a prepared trench, it should be apparent that the invention is suitable for use in other applications, such as surface applications where there is sufficient slope.
Within a prepared trench with sufficient fall, a series of concave chutes are fixed in overlapping alignment. The bottom of the trench should have a fall equal to or greater than xc2xc inch per foot. The concave chutes are fixed with their leading end upon the surface or base of the trench and their trailing end elevated so that the elevation rate of each concave chute is xe2x85x9 of an inch per foot or more and creating an effective fall within each chute of xe2x85x9 per foot or more. The concave chutes may be fabricated by cutting a semicircular section from commercially available pipe of plastic, metal or other suitable material; or preferably the concave chutes may be fabricated from sheet stock of plastic, metal or other suitable material which is then bent and fixed into the necessary concave shape. The concave chutes are preferably tapered toward their leading edge so as to facilitate the collection of moisture. If desired, the drainage system may be concealed and allow overlying landscaping or construction by filling the trench containing the concave chutes with gravel.
In operation of the drainage system of the present invention moisture from the surface and surrounding soil, under force of gravity or hydrostatic pressure, enters the trench where it flows toward the overlapping concave chutes. At the leading edge of each concave chute any moisture present is collected and flows within the concave chute by gravitational force in a direction toward the trailing edge of the concave chute. Although the amount of fall within each chute is slightly less than that of the bottom surface of the trench, it has been found that there is less resistance to moisture flow within the concave chutes in comparison to that outside of the concave chute within the trench; therefore moisture within the trench, seeking the path of least resistance, is readily collected into the concave chutes rather than flowing along the trench outside the concave chutes. Upon reaching the trailing edge of a concave chute, moisture flowing within the concave chute falls within a successive concave chute and continues flowing toward the trailing edge of each successive concave chute. As the trailing edge of each concave chute overlaps the leading edge of its successive concave chute, moisture collected at the leading edge of any concave chute is isolated and prevented from re-infiltrating the soil surrounding successive concave chutes.
As an enhancement of the present invention, the concave chutes may be enclosed within a perforated pipe, to protect the concave chutes from the accumulation of silt and sediment, and to provide structural protection to prevent damage to the concave chutes. The pipe stock utilized may be any commercially available pipe of plastic, metal or other suitable material of appropriate diameter. The pipe utilized is fashioned with an opening or perforations along the lower surface of its diameter to allow the entry of moisture. Additionally, when pipe of appropriate diameter is utilized, the pipe further serves to maintain the concavity of concave chutes fashioned from resilient material.
As an additional enhancement of the present invention, a catch basin may be provided to assist in collecting moisture into the concave chutes. The catch basin extends outward laterally from both sides of the concave chutes to catch moisture from the surrounding soil and surface above and direct it toward the concave chutes. The catch basin is placed below the concave chutes and is fashioned with support tabs which emanate from directly below the concave chutes and are attached to the concave chutes maintaining the concavity and elevation of the concave chutes. Further, an oversized aperture is fashioned in the catch basin at the leading edge of each concave chute, through which a tab fashioned upon the leading edge of the concave chute passes; in addition to mechanically fixing the leading edge of the concave chute, this oversized aperture allows percolating moisture from below the catch basin to be collected into the concave chute.
A final enhancement of the present invention is the incorporation of drain support/diverters at intervals along the length of the drain system. Each drain support/diverter, is driven into the base of the trench and supports the protective perforated pipe. These drain support diverters are fashioned of plastic, metal or other suitable material, have a semi-circular recesses formed in their upper ends and are designed to span the width of the trench. As each drain support/diverter is driven into the base of the trench and spans the width of the trench, moisture unable to traverse the drain support/diverter is forced into collection by the concave chutes and prevented from flowing toward the discharge point within the trench outside of the concave chutes.
While these drain support/diverters are utilized to capitalize upon the isolating effect of the present cascading chute drainage system, they are also suitable for use in connection with other perforated pipe drainage systems, such as the french drain systems hereinbefore described, to force water flowing along the perforated pipe to enter the pipe at intervals along its length.
Other objects, advantages and novel features of the present invention will become apparent from the following drawings and detailed description of the preferred embodiments.